Ignition Conditions Research Articles

Atomic simulation of surface damage of fused silica under laser irradiation

Fused silica optical element is the core component of the inertial confinement nuclear fusion ignition device. Due to the requirement of ignition conditions of the device for high power laser, the damage to fused silica optical element under strong laser is the key to restricting the operation of the ignition device. Therefore, the study of the surface damage of fused silica irradiated by laser is crucial to the development of the ignition device for inertial confinement nuclear fusion. In this paper, large-scale non-equilibrium molecular dynamics simulation method and micro-structure analysis technology suitable for dynamic process are proposed to study the damage process of fused silica surface under laser loading. Based on the theoretical study of high-temperature plasma fireball model, the damage of high-temperature fused silica plasma ball to surface is simulated. By tracking the local structure, temperature distribution and surface morphology, the factors affecting the surface damage of fused silica are analyzed. Our research results show that the size, distance from the surface, and temperature of high-temperature fused silica balls have important effects on the surface damage. We find that there are two different damage modes under the combined effect of the above factors. One is related to a rapid damage process, generating U-shaped voids and no further obvious damages after the surface spraying, and the other is dependent of a slow damage process: continuously expanding and resulting in a larger damage area. The surface morphologies formed by these two damage modes are consistent with the two typical damage morphologies observed in the experiments. This research can provide a guidance for understanding the complex damage process in fused silica under laser irradiation.

Experimental research on flammability characteristics and ignition conditions of hybrid mixture emissions venting from a large format thermal failure lithium-ion battery

When the concentration of gas is below its lower flammable limit and the content of the particles is below its minimum explosible concentration, it can be explosible. Thermal abuse tests for 50 Ah lithium-ion batteries were conducted under an inert atmosphere. The battery failure venting emissions were collected and their composition was identified previously. It still needs further research for the flammability characteristics and ignition conditions for hybrid mixture emissions venting from a large format lithium-ion battery thermal failure. In this study, the likelihood, severity, and kinetics of the batteries' hybrid mixture emissions flammability have been researched. To analyze battery emission flammability characteristics, five indexes have been investigated; they are ignition temperature (Tig), ignition time (τig), maximum explosion pressure (Pmax), pressure rise maximum rate ((dP/dτ)max), and size-normalized maximum rate pressure rise (KSt). Based on quantitative analysis for the hybrid mixture flammability characteristics, it indicates that particle size and gas content can impact hybrid mixture emission flammability characteristics. As for the mixture with finer particles, the optimum combustion condition of the particle and gas concentration pairs were 0.3 and 0.7. The ignition temperature for the optimum combustion conditions was 495 °C. The pressure rising velocity was 23 Mpa/s during ignition. High solvent content and low particle concentration are the conditions for optimum combustion. This indicates that the gas admixture solvent plays a major role in the combustion kinetics of the mixture emission. This research offers a fundamental perspective and provides preventive and protective thermal safety designs that are more suitable for large format commercial battery thermal systems.

Critical conditions of forced ignition in Ni-Al, Ti-Al powder systems under solid-phase synthesis

A theoretical study of the critical conditions of forced solid-phase ignition in Ti-Al, Ni-Al systems was carried out. Based on the analysis of the non-stationary diffusion equation with moving boundaries, the critical powers of the heating source and the corresponding critical temperatures were determined during the formation of NiAl, TiAl3 intermetallic compounds using the state diagrams of these binary systems. The diffusion activation energies, frequency factors, particle sizes, and heat removal conditions were considered as variable parameters. The diagrams of critical parameters which relate the corresponding specific heating powers with the indicated values were constructed. It has been established that for the same values of the parameters and under identical synthesis conditions, the critical temperatures in these systems differ by more than one hundred degrees. The latter is associated with a significant difference in the width of the solubility region for the corresponding compounds of the composition NiAl, TiAl3. The performed analysis allows separating the modes of isothermal sintering and thermal explosion which makes it possible to control the thermal and diffusion modes of synthesis. The comparison of the calculation results with the experimental data showed their satisfactory agreement.

Experimental and kinetic modeling study of tetramethylethylenediamine: A promising green propellant fuel

Tetramethylethylenediamine (TMEDA) is a promising green propellant fuel and reactivity promoter. However, the reactions between TMEDA and O2 are usually overlooked under ignition conditions. In this study, significant low-temperature reactivity was observed for 2%TMEDA/O2 mixtures, and autoignition could occur even at 470 K. To probe the chemical kinetics of TMEDA/O2, ignition delay times were measured in a rapid compression machine and a high-pressure shock tube. TMEDA pyrolysis products were also obtained in a single pulse shock tube. The autoignition of TMEDA/O2 in rapid compression machine experiments showed multi-stage heat release, a characteristic which became more obvious at oxygen-lean conditions. During the oxidation experiments, a non-Arrhenius temperature dependence of ignition delay time was observed. A chemical kinetic model of TMEDA was developed hierarchically, based on current reaction kinetics knowledge about hydrocarbons, small amines and NOx. Ignition delay times and pyrolysis products measured in this study, along with experimental data on small amines from the literature, were used to validate the kinetic model, which generally produced good predictions across different temperature, pressure and equivalence ratio conditions.

Physical aspects of fire and explosion hazard of combustible dust. Part 1.Ignition

Based on the fundamental combustible systems properties - distributed nonlinear energy sources and flow connection between the environment elements - an analysis of various combustion dust modes is presented. Depending on the ratio betweencharacteristic burning times (thermokinetic characteristics) and heat transfer (scale characteristics), limiting modes are considered as self-ignition, diffusion combustion and auto-wave combustion. Unlike gases, for dusts all the characteristics of ignition and combustion essentially depend on the internal system scales - particle sizes and distances between them. In presented part of the study, the critical ignition temperature dependences and the ignition delay time on all physicochemical dust parameters are analyzed. It is shown that these characteristics for various fuels can be described in a unified way, based on the laws of oxidation (linear and parabolic), with the systematizing parameterfbeing the ratio of the solid fuel reaction surface to the external heat exchange surface.
 Taking into account the parameter f, which is the ratio of the dust reaction surface to the external aerosuspensionheat exchange surface of the dust, the critical ignition conditions are obtained in the form of a criterion similar to the single particles ignition. It is shown that it can be used for dust with both a linear and a parabolic oxidation law. Different fuels react in the same way to a change in f, which does not contain fuel characteristics and reflects thedustheat accumulation capability. Thus, the ignition temperature is a linear function of 1/lnf, and the induction period is 1/f.
 The ignition temperature and ignition delay time are not physical or chemical, but are relativedust activity properties in relation to the their ignitionprocess. After all, they depend on the size of the reaction vessel.

Schlieren imaging and spectroscopic approximation of the rotational-vibrational temperatures of a microwave discharge igniter with a resonating cavity.

A microwave discharge igniter (MDI) with a resonating cavity was developed and optimized for practical applications in an internal combustion engine. In contrast to the typical microwave ignition, the resonating cavity of the MDI induces a discharge through dielectric resonance. Its source of microwave (MW) is a 2.45GHz semiconductor oscillator that is capable of numerous oscillation patterns. To verify and demonstrate the optimum ignition performance and combustion, we varied the oscillation parameters (signal factors) of the MW to optimize the performance of the MDI using the Taguchi method. Plasma spectroscopy was used for ignition condition analysis. Two sets of microwave pulses, a first pulse followed by a second set of pulse bursts, were used to ignite a propane-air fuel. The flame kernel growth rate and O I species generation were used as the response outputs, which were obtained, respectively from Schlieren imaging and emission spectroscopy experiments. The extended pulse periods and higher MW pulse numbers of the second set of pulses improved the response outputs of the MDI. To further analyze the effect of MW oscillation patterns on plasma properties and performance, measurements were done on MW superimposed operation with the high-voltage ignition from spark plugs. The MW transmission on a typical spark plug enhanced the air plasma ignition. Higher input MW energy and more extended MW pulse widths results in increased spectral intensity and radical generation of OH, O, and N 2. An inverse relation between the temperature and spectral intensity functions of the MW pulse width was observed, which was attributed to the cutoff density of the MW-enhanced plasma.

Effects of aluminum powder additives on deflagration and detonation performance of JP-10/DEE mixed fuel under weak and strong ignition conditions

As a high-density hydrocarbon fuel with good comprehensive properties, JP-10 is widely used in scramjets and detonation engines. Previous work has improved the ignition susceptibility and reduced incomplete combustion product concentration of JP-10 liquid fuel by blending diethyl ether (DEE). However, the density and bulk calorific value of hydrocarbons do not increase indefinitely with the increase of the ring structure, and the low temperature properties of the fuel gradually deteriorate with the increase of density. Therefore, adding metal dust with higher combustion calorific value to improve the energy density of mixed fuel is a new solution. In the present work, the deflagration and detonation properties of multiphase mixed fuels obtained by adding three aluminum powders with different morphologies and particle sizes (flake aluminum powder, small spherical aluminum powder, large spherical aluminum powder) to the JP-10/DEE mixed fuel were investigated. Under weak ignition conditions, the addition of aluminum powder increases the average burning rate of the multiphase mixed fuel and flame intensity significantly. The increase rate of the flame intensity when spherical powders are added is lower than that of the flake aluminum powder. The addition of aluminum powder is conducive to the early acceleration of deflagration, and the flame intensity reaches a high level earlier. Although the aluminum powder increases the energy of the reaction system, it also aggravates the incomplete combustion of JP-10/DEE in the oxygen-depleted state, and generates a large amount of soot. Under the strong ignition conditions, the DDT process of JP-10/DEE/aluminum powder can be divided into four stages: the slow propagation stage, shock wave formation stage as a result of compression wave superposition, coupling evolution stage of shock wave and flame front, and the detonation stage, respectively corresponding to four different pressure wave pattern. The strong ignition method greatly accelerates the evaporation of JP-10/DEE and the melting of the aluminum core in the initial stage, so that the multiphase mixture quickly changes from a slow propagation mode to a strong deflagration mode.

Big Data-aided Study of the Physical Process of Volume Ignition

Volume ignition is a method of igniting a fuel as a whole by simultaneously achieving ignition conditions throughout the fuel zone. The basic criterion for ignition is that the thermonuclear energy is greater than the energy leakage at the fuel boundary, resulting in self-sustaining heating and deep combustion. Deuterium-tritium fuels are wrapped in medium to high Z media to reduce radiative leakage and achieve lower-temperature holistic ignition and non-equilibrium combustion, ultimately allowing the fuel to achieve high combustion efficiency. Volume ignition is the use of energy balance relations under the local thermodynamic equilibrium approximation to establish the energy balance equation for thermonuclear systems, and the system ignition threshold is obtained by solving this equation. By understanding the physical process, we believe that the non-equilibrium process is universal to the volume ignition process. Changes in external factors (density, boundaries, albedo, etc.) at the moment of ignition can have a significant impact on the development direction of the system, and an ignition system with a large surface density can nevertheless withstand a large amount of reverse work and continue to burn. The design of the ignition target tries to avoid these factors through margin design, but conversely, the rational use of these laws can further improve the design margin of the capsule. With the aid of big data, the volume ignition method is easier to calculate and has a shorter iteration time. The traditional way is to propose a model, set the material, and then perform the calculation while using big data can set any model and material for calculation. In this paper, a simple comparison will be made to find out that the efficiency of the physical design of a volume ignition target will be effectively improved with the aid of big data. Volume ignition targets can be used not only in Z-pinch-driven systems but also for laser-driven volume ignition.

Minimum Values of Voltage, Current, or Power for the Ignition of Fire

Under some circumstances, fires can be ignited by electric current. The two main mechanisms for this are arcing/sparking and hot surfaces. However, it has been viewed for a long time that this will not happen if the voltage, current, energy, or power are too low. The concept of a minimum ignition energy (MIE) characterizing the ignitability of flammable gas atmospheres is well established, and extensive published data are available. However, a corresponding ignition energy criterion for solids (minimum energy fluence) has been shown not to be valid. Some additional systematic experimental data (minimum voltage, current, power) have been collected for the spark ignition of gas atmospheres. However, it is found that the results are strongly dependent on the test conditions. Exceedingly scant data are available for the minimum electrical conditions for ignition of solid materials. Two concepts—intrinsic safety, and Class 2 or 3 power supplies—have long been available as safety measures against ignition from electrical circuit sources. However, ignition has been demonstrated to be possible with Class 2 power supplies. Ignition of solid material from a 1.2 V battery has been documented in the literature. Wide-ranging experimental research is urged to expand the knowledge base in this important area of electrical safety.

Influence of Adding Carbonaceous Fuels to Ionic Liquids on Propellant Properties.

To make ionic liquids (ILs) accessible and economical, ethylene glycol was mixed in 1-ethyl-3-methylimidazolium-dicyanamide ([EMIm]DCA) to obtain droplets that could experimentally collide white fuming nitric acid. To investigate the ignition delay (ID) time theoretically in terms of hydrodynamics, alcohol fuels and kerosene were used as combustibles, while the intermiscibility between them and nitric acid (HNO3) was calculated using the ternary phase-field method alongside finite element analysis. The specific impulses of blend fuels were calculated by a thermodynamic method and compared to ILs. When the droplet was ethylene glycol/[EMIm]DCA with a 2.1 mm diameter and a 1.69 m/s colliding velocity, the ID time was the shortest. Kerosene was not an applicable additive for [EMIm]DCA owing to its lower intermiscibility with ILs and HNO3 than alcohol fuels; alcohol fuels, however, were appropriate. The concentration of ethylene glycol in the oxidizer pool increased faster than the concentration of propylene glycol, triggering more rapid hypergolic ignition in the first 50 ms. The protocols regarding the hypergolic ignition conditions were verified, i.e., the size of the droplet had to be minute when the colliding velocity was as fast as possible; this was carefully calculated using ethylene glycol. According to thermodynamic calculations, the addition of alcohol fuels can improve the specific impulse of fuels, with ethylene glycol performing the best. The feasibility of adding alcohol fuels to ILs was confirmed via experiments and thermodynamic computations, with the simulation results providing some guidance on selecting the experimental or engineering conditions or both.

Benchmarking Between COMSOL and GPYRO in Predicting Self-Heating Ignition of Lithium-Ion Batteries

Recent studies have shown that self-heating ignition is a possible cause of fires when Lithium-ion batteries (LIBs) are stacked in large numbers, for example, during storage. The understanding of this ignition type is limited, and most current studies are based on numerical modelling. The different modelling tools found in the literature differ in their assumptions, capabilities, and resources needed, and may provide significantly different predictions. This study presents a benchmarking between COMSOL Multiphysics, which is one of the most prevailing tools used in modelling thermal-electrochemical behaviour of LIBs, and Gpyro, which is widely used in modelling ignition of solid fuels. Four case studies are designed with increasing levels of complexity: (1) just chemical kinetics at the microscale, (2) just heat transfer at the mesoscale, (3) self-heating behaviour at the mesoscale for coupled chemical reactions and heat transfer of a single cell, and (4) four-cell ensemble for multiphysics at a larger scale. The results of scenarios #3 and #4 are also compared to experiments. The results show that although COMSOL and Gpyro have significant differences in their assumptions and resources needed, both tools can accurately predict the critical conditions for ignition for self-heating, which validates their use to study the safety of LIBs.

Modeling Hypergolic Ignition Based on Thermal Diffusion for Spherical and Cylindrical Geometries

ABSTRACT A linear model for predicting the ignition delay time of hypergolic ignition is presented based on thermal diffusion theory. The heat released by the hypergolic reaction is assumed to diffuse through a given length scale while being governed by a heat source in the form of an Arrhenius equation. A linearized approach is used to reach analytical expressions for the ignition delay times, defined when the temperature change at the reactants interface drastically increases, diverges, or tends toward infinity. Ignition delay times for three different geometries, cartesian, cylindrical, and spherical, are derived and compared. The results show that, for spherical coordinates, the ignition depends on a critical condition, which is based on material and chemical properties and geometry. A prediction of the ignition condition for all cases where one of the reactants is a droplet/particle is given. The ignition process is analyzed based on non-dimensional parameters in order to understand the behavior of the temperature change during ignition. The results obtained are consistent with results presented in the literature. In addition, a prediction for ignition delay times is provided.

Influence of Incident Shocks on Flame Characteristics in the Strut-Equipped Supersonic Combustor

In this paper, under incident shock waves, the flame characteristics of the strut-equipped supersonic combustor fueled by liquid kerosene are investigated by numerical simulation and experimental means in operating cases of Mach . During this process, the Mach number at the combustor entrance varied from 2.0 to 2.8, and a 14 deg wedge was installed at the isolator inlet as an incident shock simulator. A position-adjustable thin strut was used to optimize the ignition efficiency, and flame propagation was captured and reproduced using a visualization window mounted on the combustor side wall. The conclusions drawn from the study could reduce potential hazards for flight experiments. The simulation found that with the addition of the incident shock wave, the asymmetric shock wave system and the discontinuous acceleration regions were formed in the initial flowfield, which caused the relative position between the strut and wedge to have a significant effect on ignition. Experiments showed that when the two were mounted on the same side, the incident shock wave weakened the ignition conditions, preventing the formation of a global flame within the combustor. After changing the wedge installation direction and reducing the inlet Mach number, the effect of the flame characteristics affected by the incident shock wave was easier to capture. The flame kernel appeared at the strut tail, the combustion heat release area became more concentrated, and the flame development was accelerated. The results showed that the incident shock wave kept the flame oscillation frequency around 170 Hz, and the combustor pressure rise performance in the steady state was almost unchanged. Overall, the ignition delay of the combustor is increased, but the engine thrust is hardly affected by comparison with the ideal situation.

Combustion characteristic of low calorific gas under pilot ignition condition—Exploring the influence of pilot flame products

Low calorific gas (LCG) is a huge thermal energy resource, but its utilization is poor due to the low reactivity and a tendency of high NOx emission. Present work proposed to combine the pilot ignition and air staging approach, to respectively overcome the difficulty in LCGs ignition and reduce its NOx emission. Experiment and numerical simulation were conducted to explore combustion characteristic of LCG during pilot ignition. Some previous proposed kinetics models for CH4 or CO combustion were evaluated that whether they capture the NO or H2O influence, respectively, within this complex flue gas atmosphere, and the mechanisms were further explored. Adding 0.04 vol% NO reduces the ignition temperature of CH4 based LCG from 750 to 510 °C under pilot ignition condition. This promotion is via a NO/NO2 cycle of NO + HO2→NO2+ OH andCH3+ NO2→CH3O + NO, to enhance CH3 oxidation rate by ∼ 30 times. In that cycle, the NO formation (NO2 consumption) rate is higher than the NO2 formation (NO consumption), causing only NO but no NO2 was preserved in flue gas under pilot ignition condition. The effect of adding NO to CO based LCG is dependent on H2O presence, where it makes no difference without H2O presence, but has an improvement on “moist gas” reactivity. Neither the commonly used kinetics models of CH4 combustion nor those for CO contained syngas gas can predict reactivity of “dry CO contained LCG” under pilot ignition condition.

Inward-propagating cylindrical flames under different ignition conditions

Inward-propagating cylindrical flames are studied numerically by high-resolution simulations using a one-step Arrhenius kinetics. Emphasis is placed on the effect of shock waves on the flame propagation by setting initial ignition conditions with and without shock wave. It is found that without initial shock wave, the inward-propagating flame propagates initially at a constant speed, while in the later stage of the propagation, it shows a small-amplitude oscillatory motion. When the shock wave initially introduced is medium, a large-amplitude oscillatory motion is caused by the interaction of shock waves with the inward-propagating flame. Moreover, autoignition occurs at the center and develops outwardly into a cellular flame. However, as the introduced shock wave is strong, autoignition created at the center evolves outwardly a cellular detonation.

Characteristics of Premixed Flames of Hot and Diluted Mixtures

ABSTRACT Internal recirculation of product gases and mixing with fresh reactants, to form a hot and diluted combustible mixture, has been demonstrated to result in lower pollutant emissions. With sufficient amount of product gas recirculation, the mixture can reach above its auto-ignition temperature with low oxygen mass fractions (<4 wt%), resulting in distributed reactions instead of a flame. Some of the technologies with this feature are Moderate or Intense Low oxygen Dilution (MILD) combustion, FLameless OXidation (FLOX) and Colorless Distributed Combustion (CDC). However, if the amount of product gas recirculation is not enough and the auto ignition condition is not reached, premixed reactants of the hot and diluted mixture can be established. In this study, characteristics of such hot and diluted mixtures is studied which include the ignition delay time and the flame attributes such as laminar flame speed, S L and thermal flame thickness, . A perfectly stirred reactor (PSR) using the hot and diluted mixture as the inlet was further examined to simulate the main combustor and combustion efficiency η, and CO and NOx emissions were obtained. The investigations are performed at different product gas recirculation amounts , equivalence ratios ϕ and operating pressures P, using chemical kinetic simulations. The thermo-chemical state of the recirculated product gases was obtained using a PSR with varying residence times (τ) to simulate different “burntness” levels (smaller τ simulates lower “burntness” level). The hot and diluted mixture temperature is higher, while oxygen and fuel mole fraction are lower for higher ξ, ϕ, P, and τ. Radical species’ mole fraction is higher for higher ξ, ϕ, and lower P, τ. Lower is observed for higher ξ, ϕ, P and smaller τ. Higher S L is observed for higher ξ, ϕ and lower P. Lower is observed for higher ξ, ϕ and P. S L and are found to be higher or lower with variation in τ, depending on ξ, ϕ and P, owing to variation in temperature and radicals’ concentration. Higher η is observed for higher ξ, P, lower ϕ, τ, and higher residence time of gases (τ reac ) inside the main combustor. Lower CO is observed with increase in ξ, P and decrease in τ, while exhaust NOx increases with ϕ and mostly remains unchanged with increase in ξ, while inconsistent trends are observed with change in P and τ.

Experimental study of the ignition conditions for self-sustained smouldering in peat

Tackling peatland wildfires, the largest fires on Earth in terms of fuel consumption, is an emerging combustion topic in the context of climate change and environmental protection. The understanding of the basic mechanisms of ignition of peat to initiate self-sustained smouldering is essential in the development of mitigation technologies, but it is not well studied yet in the literature. In this research, laboratory experiments were conducted to improve the understanding of how peat conditions (moisture content and bulk density) and the ignition protocol influence the ignition probability. A new ignition protocol was developed by stopping the heat source when 10% mass of the sample is lost. This mass-based ignition protocol was found to be robust to initiate self-sustained smouldering in peat samples for a wide range of soil conditions. By using the new ignition protocol, experiments using peat samples of moisture content from 100% to 180% with a range of bulk densities were conducted to investigate how these properties together influence the critical ignition conditions. Results show that although the moisture content plays a major role in the ignition probability, bulk density is also important. Increasing peat density increases the mass of water in a unit volume. This increase of heat sink makes the ignition more difficult. These findings contribute to studying smouldering peat fires and improve the understanding of ignition.

A Comparative Study on the Mathematic Models for the Ignition of Titanium Alloy in Oxygen-Enriched Environment

Metallic materials are always suffered from the risk of combustion when serviced under some extreme conditions such as high temperature, oxygen-enriched enrichment, and high-speed friction. Although different mathematic models have been proposed but it is still a challenge for accurately describing the ignition conditions of metals under the extreme conditions, which is of great significance for the safety-use of materials. In this paper, the mathematic models based on Semenov and Frank-Kamenetskii theory were introduced into describing the effects of size, oxygen concentration, and oxygen pressure on the ignition temperature and critical oxygen pressure of TC17 alloy. The results showed that the critical oxygen pressure of TC17 alloy increased with the increase of size, which was fitted well with the Frank-Kamenetskii model. As a comparison, the critical oxygen pressure was size independent in the Semenov model, which was inconsistent with the experimental data. For the Frank-Kamenetskii model, the fitting results showed that the activation energy, reaction order, as well as the adsorption coefficient of TC17 alloy were determined to be 99.23 kJ/mol, 1.69, and 4.01 MPa−1.69 respectively. Based on above, the ignition temperature of TC17 samples with different sizes were predicted well by the Frank-Kamenetskii model with the relative error within 3.58%, which could be suitable for describing the critical ignition conditions of bulk metallic materials under complex environment.

Investigation of proton-boron-11 degenerate fuel pellet plasma ignition conditions by proton beam driver in fast ignition process

Investigation of proton-boron-11 degenerate fuel pellet plasma ignition conditions by proton beam driver in fast ignition process

Combined experimental and numerical studies on soot characteristics of diesel sprays with split injection strategies

Experimental and numerical studies on the soot characteristics of Spray A flames were conducted with a focus on the effects of different split injection strategies in high-pressure high-temperature vessels within the engine combustion network. Three high-speed imaging techniques were used to obtain the transient information of flame evolution. Schlieren was applied to identify the spray boundaries and spray penetration. Moreover, a combined extinction and radiation technique was applied to quantify the spatial soot and temperature fields simultaneously. Finally, high-speed OH* chemiluminescence was applied at the baseline condition to measure the temporal high-temperature flame evolution. To substantiate the analysis, the experimental results were compared with the computational fluid dynamics (CFD) predictions from a Reynolds-averaged Navier Stokes approach with Unsteady Flamelet Progress Variable combustion and a two-equation soot-in-flamelet models, which qualitatively reproduced the experimental results.According to the chosen split injection strategy, dwell and first-injection pulse durations were varied. For all cases, the ignition delay (ID) and soot production of the second-injection pulse were shorter and higher than those of the first one, respectively. A slight change in the experimental soot production was observed when the dwell time was changed. The CFD calculations revealed a small reduction in the ID of the second pulse with long dwell times, which was due to variations in the interaction between the newly injected fuel and combustion recession. However, the effect of dwell variation was extremely small to produce significant differences in the evolution of the second pulse, neither in combustion nor in soot production. With regard to the duration of the first injection, no effect on the experimental soot production of the second pulse was observed despite noticeable differences due to the first pulse. The CFD results indicated that because of the quasi-steady flow and combustion process near the nozzle along the first injection, the evolution of the spray in the region close to the nozzle was identical in all first-pulse-duration cases, with differences only occurring at the tip of the first pulse jet. Thus, the second pulse evolution occurred under identical conditions for ignition and soot production. Although the sensitivity to both dwell and first-pulse durations was low, the CFD analysis highlighted the important effects of both end-of-injection wave propagation and combustion recession on the ignition and soot production of the second pulse.